One organism's flesh is another's meat -- there are even insects that can digest wood -- but no animal has ever evolved that can derive any nutritional value from bones, AFAIK. (Tasmanian devils (http://en.wikipedia.org/wiki/Tasmanian_devil) ingest bones but I'm pretty sure they pass through undigested.) Why is that?

lieu

08-27-2007, 12:29 PM

Both ancient and modern hyenas were unique in their ability to crush and digest bone—an extremely advantageous adaptation that also leads to distinct jaw and tooth shape and function. (http://www.usc.edu/hsc/dental/update/march07/RESEARCH_hyenas.html)

Great Dave

08-27-2007, 12:30 PM

Wood is made of carbohydrates that can be broken down by bacteria living in the gut of insects. The last bit of bone that does not get digested is mineral, and has no nutritional value.

ETA: Hyenas are probably digesting the tissue inside the bones, not the entire bone.

lieu

08-27-2007, 01:11 PM

Anecdotal, but on a recent paleontological dig in Utah in the Morrison (Jurassic, near Arches N.P.) hosted by BYU, a museum director and professor pointed out borings in dinosaur bones and how the fact they worked from the underside up could be used to reconstruct the original orientation before a period of fluvial redeposition. Here's (http://jpaleontol.geoscienceworld.org/cgi/content/full/81/1/201) an article that alludes to something similar.

"Osteocallis mandibulus n. igen. and isp. is described in dinosaur bones from continental deposits of the Upper Cretaceous Maevarano Formation of Madagascar and the Upper Cretaceous Kaiparowits Formation of southern Utah. O. mandibulus consists of shallow, meandering surface trails, composed of numerous arcuate grooves, bored into compact (cortical) bone surfaces, and is tentatively interpreted as a feeding trace."

coffeecat

08-27-2007, 01:17 PM

Sardines are a good source of calcium because people eat them bones and all.

OtakuLoki

08-27-2007, 01:29 PM

Another contrarian datapoint: There were no remains found with, on nor near the wreck of the Titanic. Nor associated with other bathyspheric wrecks that have been investigated since then: Bismark, Hood, the Midway ships. My gut reaction is that something had to have eaten them, but I don't think that there's any evidence for what that mechanism may have been.

BTW: Great Dave, unless I'm misremembering it, my copy of Young's Mammology does claim that Hyenas take nutrition from the bones themselves, not just the tissues in the bone. I'll dig it out to check.

Spoke

08-27-2007, 01:51 PM

Another contrarian datapoint: There were no remains found with, on nor near the wreck of the Titanic. Nor associated with other bathyspheric wrecks that have been investigated since then: Bismark, Hood, the Midway ships. My gut reaction is that something had to have eaten them, but I don't think that there's any evidence for what that mechanism may have been.

Interesting. Might the pressure at those depths have a softening effect on the bone, thus making it more palatable to sea critters?

rowrrbazzle

08-27-2007, 01:53 PM

The answer to every question beginning "Why don't they..." is always "Money". :)

Or to put it another way, there are lots of other sources of calcium that are easier to ingest. So generally the investment in maintaining a biological system that can digest bones is greater than other ways of getting calcium is not worth the trouble.

However, just last night I saw an episode of "Blue Planet" that showed the bones of a whale at the bottom of the ocean covered with colonies of bacteria or very small animals working away at the bones.

OtakuLoki

08-27-2007, 02:09 PM

Interesting. Might the pressure at those depths have a softening effect on the bone, thus making it more palatable to sea critters?

I don't believe it's that. Forex ISTR that when the wreck of the Edmund Fitzgerald was being explored recently there had been a report that they'd found human remains near the ship. But the remains couldn't have been any of the crew - because it was wearing lifepreserving equipment from the 1880s. That implies to me that deep fresh water environments lack the ecosystem to disgest bones that an ocean has.

Which isn't unreasonable when you consider that most deep water fresh water bodies are relatively young, and would need a lot of radiative evolution to fill those niches - since transport of the ocean varieties would be percluded by the huge hazard of osmotic differences between living in fresh water and living in salt water. Plus the difficulty in having a deep water creature surviving to get to or near surface pressures, then adapting back down to the deep water again.

Oh, I was wrong it's Vaughan's Mammology I've got, not Young's. Okay, a quick run through has a discussion of the Hyenas being adapted to crushing and eating large bones, but not specifying that they're taking nourishment from the bone matrix, or just the tissues distributed through the matrix.

GaryM

08-27-2007, 02:17 PM

Do deer antlers count as bone? I know that mice and other rodents gnaw on shed antlers, but I'll admit that I don't know if they actually "eat" them.

Crotalus

08-27-2007, 02:28 PM

Reptiles definitely ingest and to some degree digest bones. Based on a fair amount of experience with the feces of rodent-eating snakes, I would say that they have more trouble digesting hair than bones. I'm not sure how much nutritional benefit reptiles derive from the bones they eat, but I believe that they get calcium from them.

Contrapuntal

08-27-2007, 02:33 PM

It may be the case that some deer eat baby birds for the calcium in their bones.

This (http://news.nationalgeographic.com/news/2003/08/0825_030825_carnivorousdeer.html) article was mentioned in another thread, on hooved predators. It would appear the deer are specifically eating the bones of the chicks for their calcium content. It's still being researched and isn't fully understood yet, though.

ETA: Dangit. Beaten to it.

Lemur866

08-27-2007, 02:40 PM

There's a couple of things here.

Bones contain both minerals and protein. Once the protein is gone you can't get anything more than minerals from what's left over.

Plenty of animals eat bones, and they digest the protein fraction. Then they excrete the leftover minerals, because they don't need them. There's only so much calcium a hyeana can use.

Small bones are almost always eaten...tail bones, vertebrae, ribs, parts of the skull, phalanges, and so forth. But heavy limb bones like the femur, tibia and humerus might be too strong for most predators to crack. They'll suck out as much as possible, but can't crush the bone itself. And of course, small animals are eaten whole.

So when you come across a bone out in the forest, there's usually nothing digestible left except the mineral fraction. And nothing will eat that, unless they need those particular minerals. So it's not correct that bones don't get eaten, they do. But only the digestible portion of the bones can be digested. Wood is made of cellulose and lignin. There are organisms that can digest cellulose, and even lignin, but you can't digest calcium and use it as an energy source.

OtakuLoki

08-27-2007, 02:47 PM

Bones contain both minerals and protein. Once the protein is gone you can't get anything more than minerals from what's left over.

Just out of curiousity - how much of the shape of the bone is due to the structure imparted by the proteins? What I mean, it seems to me that if bones are calcium heavy protein matrices, as long as there's a recognizable shape, there's bound to be still some protein fractions available there.

Granted, for most aninamls, because of the difficulty of breaking that matrix into smaller digestable pieces is hard, there are easier (and less energy intensive) sources of protein fractions. But that doesn't mean that they don't have any nutritional value.

Spectre of Pithecanthropus

08-27-2007, 04:12 PM

Both ancient and modern hyenas were unique in their ability to crush and digest bone—an extremely advantageous adaptation that also leads to distinct jaw and tooth shape and function. (http://www.usc.edu/hsc/dental/update/march07/RESEARCH_hyenas.html)

Hyenas? Even a housecat can easily chew its way through a small rodent. I had always been curious about the exact process a cat follows when eating prey, so I looked it up on YouTube. Surprisingly, if the prey is small enough, the cat's likely to just eat it head to tail, the way you or I might eat a hotdog.

Fear Itself

08-27-2007, 04:19 PM

Are antlers made of the same stuff as bones? Because there is some critter in the forest that eats fallen moose antlers in Alaska. If you don't find them soon after they are shed, they will likely be gnawed on.

Schuyler

08-27-2007, 04:22 PM

Try a Google search with "whale bones monterey" for articles and pictures of worms that are devouring the bones of a deceased whale - here's an example article: "Whale carcass yields bone-devouring worms (http://www.mbari.org/news/news_releases/2004/whalefall.html)"

Micro Dot

08-27-2007, 04:25 PM

Wasn't "The Octopus" a book about how Hormel used animal bones in various products. Ground fine enough, the bones add nutritive calcium to hot dogs.

smiling bandit

08-27-2007, 04:26 PM

Just out of curiousity - how much of the shape of the bone is due to the structure imparted by the proteins? What I mean, it seems to me that if bones are calcium heavy protein matrices, as long as there's a recognizable shape, there's bound to be still some protein fractions available there.

The protein is mostly in the marrow, not the bone tissue itself. The bone tissue has very few, if any, calories to extract.

Dervorin

08-29-2007, 04:36 AM

Lammergeiers are known to drop bones to shatter them and then eat the fragments (http://www.bbc.co.uk/nature/wildfacts/factfiles/3101.shtml).

And just how would you go about eating an invertebrate's bones? :D

Blake

08-29-2007, 05:06 AM

Bones contain both minerals and protein. Once the protein is gone you can't get anything more than minerals from what's left over.

Actually most of the calories in bone are on the form of fat. The marrow is one of the purets forms of fat on an animal carcass.

Just out of curiousity - how much of the shape of the bone is due to the structure imparted by the proteins?

All of it. The protein is laid down first and the calcium is then attached to the protein, rather like hanging papier mache over a wire frame. The wire gives the shape and the mache just fills in the spaces.

You can if you want soak a boine in a dilute acid solution for a week to remove all the calcium and then remove what looks like the original bone, except that you can now tie it in knots. Removing the calicum has no effect at all on the shpe of the bone.

What I mean, it seems to me that if bones are calcium heavy protein matrices, as long as there's a recognizable shape, there's bound to be still some protein fractions available there.

Depends what's happened to it. If the bone has been enzymatically digested then proteins will all have been solubilised and stipped away. That leaves the clacium matrix with zero protein, essentially the reverse of what happens if you acid treat a bone. Same shape, no protein.

The protein is mostly in the marrow, not the bone tissue itself. The bone tissue has very few, if any, calories to extract.

The protein is mostly in the bone, the marrow contains a sizable amount of pratein but its mostly fat and occupies relatively little of the bone volume. In addition the bone contains blood vesslels , fats and other miscellaneous inclusions. Bone as a tissue consequently has quite a few calories, although they can be hard to extract.

As for the OP, your undertsanding is all wrong. Lots of animals, like devils, eat bones, and they don't pas through undigested. If that were the case why would they bother to swallow them? The bones are digested and all the usable nutrients are extracted. The useless stuff is then excreted. This is no different to what humans do when eating corn, and you wouldn't claim that humans don't digest corn.

Spoke

08-29-2007, 08:11 AM

Try a Google search with "whale bones monterey" for articles and pictures of worms that are devouring the bones of a deceased whale - here's an example article: "Whale carcass yields bone-devouring worms (http://www.mbari.org/news/news_releases/2004/whalefall.html)"
What freaky critters:
The scientists were initially puzzled by the fact that all the worms they collected were females. However, while examining the two- to seven-centimeter-long female worms under a microscope, they discovered that most females had dozens of microscopic male worms living within their bodies. These male worms looked as if they had never developed past their larval stage—their bodies still contained bits of yolk—but they also contained copious quantities of sperm.

Contrapuntal

08-29-2007, 08:32 AM

Try a Google search with "whale bones monterey" for articles and pictures of worms that are devouring the bones of a deceased whale - here's an example article: "Whale carcass yields bone-devouring worms (http://www.mbari.org/news/news_releases/2004/whalefall.html)"Why do you suppose they only whale bones? How can the researchers be sure of that?

Blake

08-29-2007, 07:03 PM

Why do you suppose they only whale bones? How can the researchers be sure of that?

Nobody is caiming they only eat whale bones, the claim is that they have only ever been found eating whale bones. However they are so specialised that the only niche they could concievably fill is that of eating bones. Where else are you going to find a large, solid, protective, lipid filled structure in the deep ocean? These animals need exactly those conditions to reproduce. It is entirely plausible that they also consume the bones of other large marine organisms such as very large fish or seals, in fact it's hard to see why they would not, but whlae carcasses are probably the most common food source in the regions they inhabit.

MrDibble

08-30-2007, 06:47 AM

There's actually a term for such blubber-from-heaven - Whale Fall (http://en.wikipedia.org/wiki/Whale_fall)

Ale

08-30-2007, 07:00 AM

Another contrarian datapoint: There were no remains found with, on nor near the wreck of the Titanic. Nor associated with other bathyspheric wrecks that have been investigated since then: Bismark, Hood, the Midway ships. My gut reaction is that something had to have eaten them, but I don't think that there's any evidence for what that mechanism may have been.

BTW: Great Dave, unless I'm misremembering it, my copy of Young's Mammology does claim that Hyenas take nutrition from the bones themselves, not just the tissues in the bone. I'll dig it out to check.

The bones probably dissolved over the many decades since the sinking...

After googling a little bit I found this tidbit from Robert Ballard (http://gorhody.cstv.com/chat/121206aad.html) himself:

I do know that in the deep sea bones actually dissolved so I would not expect to find them there.

Do Not Taunt

08-30-2007, 11:49 AM

This is no different to what humans do when eating corn, and you wouldn't claim that humans don't digest corn.Why can't you digest corn? (http://answers.yahoo.com/question/index?qid=20070330205730AA7JTg4)

I get the point you're making, but people do make this very claim about whole kernels of corn (no one claims you can't digest processed corn.)